merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

1 files changed, 16 insertions, 8 deletions

diff --git a/third_party/git/diffcore-break.c b/third_party/git/diffcore-break.c
index 875aefd3febf..0d4a14964d00 100644
--- a/third_party/git/diffcore-break.c
+++ b/third_party/git/diffcore-break.c
@@ -4,6 +4,7 @@
 #include "cache.h"
 #include "diff.h"
 #include "diffcore.h"
+#include "promisor-remote.h"
 
 static int should_break(struct repository *r,
 			struct diff_filespec *src,
@@ -49,6 +50,8 @@ static int should_break(struct repository *r,
 	unsigned long delta_size, max_size;
 	unsigned long src_copied, literal_added, src_removed;
 
+	struct diff_populate_filespec_options options = { 0 };
+
 	*merge_score_p = 0; /* assume no deletion --- "do not break"
 			     * is the default.
 			     */
@@ -62,8 +65,13 @@ static int should_break(struct repository *r,
 	    oideq(&src->oid, &dst->oid))
 		return 0; /* they are the same */
 
-	if (diff_populate_filespec(r, src, 0) ||
-	    diff_populate_filespec(r, dst, 0))
+	if (r == the_repository && has_promisor_remote()) {
+		options.missing_object_cb = diff_queued_diff_prefetch;
+		options.missing_object_data = r;
+	}
+
+	if (diff_populate_filespec(r, src, &options) ||
+	    diff_populate_filespec(r, dst, &options))
 		return 0; /* error but caught downstream */
 
 	max_size = ((src->size > dst->size) ? src->size : dst->size);
@@ -286,17 +294,17 @@ void diffcore_merge_broken(void)
 					/* Peer survived.  Merge them */
 					merge_broken(p, pp, &outq);
 					q->queue[j] = NULL;
-					break;
+					goto next;
 				}
 			}
-			if (q->nr <= j)
-				/* The peer did not survive, so we keep
-				 * it in the output.
-				 */
-				diff_q(&outq, p);
+			/* The peer did not survive, so we keep
+			 * it in the output.
+			 */
+			diff_q(&outq, p);
 		}
 		else
 			diff_q(&outq, p);
+next:;
 	}
 	free(q->queue);
 	*q = outq;